I'm not a native English speaker but I'm always trying to do my best. Unfortunately I have a real problem with dates for some odd reason, I couldn't learn when was my birthday until I was 12 years old.

Anyway, as I was learning names of the months on English, and since I know some Latin from high school I noticed that English months don't match up with their Latin numeral counterparts. For example:

September - 9. month October - 10. month November - 11. month December - 12. month

While on latin septem, octo, novem and decem are words for 7, 8, 9 and 10.

So, does anyone know why is that. At first I thought it had something to do with switch from Julian to Gregorian calendar but I figured it's too small of a difference.

Anyone? :)

  • Have you done any research? Jan 8, 2014 at 22:03
  • 2
    july and august were inserted after these months were named.
    – user31341
    Jan 8, 2014 at 22:06
  • Searching origin month names yields this site (and many others)
    – bib
    Jan 8, 2014 at 22:24
  • 3
    @jlovegren actually that's incorrect - July and August were renamed, not inserted. See my answer.
    – toryan
    Jan 8, 2014 at 22:24
  • 1
    @Jim Sure have, but I notice this often, it's like I'm missing a lots of words so I can't think of good search terms for some specific topic. Like this one.
    – Jinx
    Jan 8, 2014 at 23:49

2 Answers 2


You are entirely correct as to the Latin correlation!

Centuries ago (somewhere around 753 BC according to Roman writers), there was the an early version of the Roman Calendar known as The Calendar of Romulus. (I'm not enough of a history buff to know exactly how widespread the calendar's usage was, but the Wikipedia article I linked to should cover such details)

The Calendar of Romulus consisted of ten months named as follows:

Each month had either 30 or 31 days in it. The problem was, the total number of days only added up to 304 per year; any additional days between December and Martius were not assigned to any month. Time passes, and another king, Numa Pompilius, rectifies this by adding two additional months before Martius.

Side note: If he had appended the two months on the end of December, the last five months' numbering systems would still be valid, but alas, he didn't. Why he didn't, I never learned, but I'm sure there was a good reason at the time.

Over the next centuries, the Roman Calendar gains acceptance across the world while several more minor tweaks to the calendar are applied. But as for the month naming, only two more major changes occur.

There is an urban myth that the months July and August were inserted by the two namesake Caesars into the calendar, causing the following "numbered" months to offset by two; this is not the case.

Quintilis was renamed to Iulius (or Julius, today known as July) in honor of Julius Caesar after his death. Similarly, Sextilis was later renamed to Augustus in honor of a later Roman ruler, Augustus.

  • I think there should be a global referendum for fixing this ancient mess :)
    – Jinx
    Jan 8, 2014 at 23:46
  • @Jinx Let's just cross our fingers for a global nuclear holocaust, so the survivors can re-build culture and civilization using a base 12 numbering system, a language with better rules and fewer exceptions such as Esperanto (or the language without ambiguity, Lojban), and of course, the Metric System.
    – IQAndreas
    Jan 8, 2014 at 23:57
  • I'm all with you on that except I'd use Croatian as official language :)
    – Jinx
    Jan 9, 2014 at 7:51

The Roman calendar originally had only ten months. The first month was March, and the tenth (and final) month was December. The months of January and February did not exist, and that time was part of a "monthless" winter period. These months were added to the calendar around 713BC.

Contrary to popular belief, July and August were not inserted into the calendar. They were renamed in honour of Julius Caesar and Augustus respectively. The original name for July was Quintilis, and August was Sextilis (from the Latin words for five and six).

Interestingly, the numbering remained correct for a long time, with January and February being the 11th and 12th months in the calendar. It was around 450BC when January became the first month.


  • I don’t think anyone actually knows when the year change was moved to last day of December rather than first day of March. The name January itself indicates that this month was likely not named until at the same time as or after New Year’s had been moved. It wouldn’t make much sense to have a January in the middle of the year. Jan 8, 2014 at 23:05
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    They are both great though, so I've upvoted both.
    – T.E.D.
    Jan 8, 2014 at 23:14
  • @JanusBahsJacquet That's an interesting point. The Wikipedia article for January seems a bit ambiguous - it gives the origin of the name as Janus, with the associated 'door' meaning, but later pretty clearly states that the change from March to January as the first month came a long time later. I'm not an historian, and this isn't the Roman History SE, so I'm not going to dwell on it :p
    – toryan
    Jan 8, 2014 at 23:34

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